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ABSTRACT: For silicon wire based ring resonator biosensors, we investigate the simultaneous retrieval of changes in the fluidic refractive index ∆n<sub>c</sub> and surface adsorbed molecular film thickness ∆d<sub>F</sub>. This can be achieved by monitoring the resonance shifts of the sensors operating in the TE and TM polarizations at the same time. Although this procedure is straightforward in principle, significant retrieval errors can be introduced due to deviations in the sensor waveguide cross-sections from their nominal values in the range commonly encountered for silicon photonic wire devices. We propose a method of determining the fabricated waveguide size using the group indices derived from measured free spectral range (FSR) of the resonators. We further demonstrate that using experimentally measured group index values, the waveguide size can be determined to accuracies of ± 2 nm in width and ± 1 nm in height. By using this procedure, ∆n<sub>c</sub> and ∆d<sub>F</sub> can be obtained to a precision of within 10% of the true values using optically measurable parameters, improving the retrieval accuracy by more than 3 times.
Optics Express 11/2012; 20(24):26969-77. · 3.59 Impact Factor
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ABSTRACT: We examined the electromagnetic responses of near-infrared metamaterials consisting of split-ring resonators fabricated on GaInAs semiconductor layers with different doping levels on an InP substrate. The inductance-capacitance (LC) resonances of the split-ring resonators could be controlled entirely from 52 to 63 THz by changing the carrier concentrations from 2.6×1018 to 2.7×1019 cm−3. Our results show the feasibility of semiconductor-based tunable metamaterials.
Journal of the Optical Society of America B 07/2012; 29(8):2110-2115. · 2.18 Impact Factor
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ABSTRACT: An InP-based Mach-Zehnder interferometer combined with a metamaterial layer consisting of a split-ring resonator array was constructed to measure the complex permeability of the metamaterial. At a wavelength of 1.5 μm, the metamaterial showed non-unity relative permeability induced by magnetic interaction with propagating light in the device. This method of measurement would be useful to determine constitutive parameters in such waveguide-based photonic devices, allowing us to design photonic integrated circuits that make use of metamaterials.
Optics Letters 06/2012; 37(12):2301-3. · 3.40 Impact Factor
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ABSTRACT: Room-temperature pulsed operation of a 1.3-µm wavelength transistor laser (TL), consisting of a buried heterostructure (BH) with an npn configuration and an AlGaInAs/InP multiple-quantum-well (MQW) active region, was successfully attained. A threshold base current of 18 mA (threshold emitter current of 150 mA) was obtained with a stripe width of 1.3 µm and a cavity length of 500 µm. The transistor activity as well as the lasing operation were achieved at the same time, which is essential for the high-speed operation of TLs.
Optics Express 02/2012; 20(4):3983-9. · 3.59 Impact Factor
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IEICE Transactions. 01/2012; 95-C:229-236.
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Takahiko Shindo,
Tadashi Okumura,
Hitomi Ito,
Takayuki Koguchi,
Daisuke Takahashi,
Yuki Atsumi,
Joonhyun Kang,
Ryo Osabe,
Tomohiro Amemiya,
Nobuhiko Nishiyama, Shigehisa Arai
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ABSTRACT: We fabricated a novel lateral-current-injection-type distributed feedback (DFB) laser with amorphous-Si (a-Si) surface grating as a step to realize membrane lasers. This laser consists of a thin GaInAsP core layer grown on a semi-insulating InP substrate and a 30-nm-thick a-Si surface layer for DFB grating. Under a room-temperature continuous-wave condition, a low threshold current of 7.0 mA and high efficiency of 43% from the front facet were obtained for a 2.0-μm stripe width and 300-μm cavity length. A small-signal modulation bandwidth of 4.8 GHz was obtained at a bias current of 30 mA.
Optics Express 01/2011; 19(3):1884-91. · 3.59 Impact Factor
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ABSTRACT: In this paper, the state-of-the art of long-wavelength GaInAsP/InP membrane semiconductor lasers, one of the most promising candidate light sources for optical interconnects and on-chip optical wiring between large-scale integrated circuits, is described. After an extensive review of research activities focused on laser preparation on either Si or Si-on-insulator substrate, the findings of our recent research activities on low power consump-tion lasers are presented. Specifically, our interest was set on the low-damage fabrication of strongly index-coupled grating, which is generally opted forDFB and distributed reflector (DR) lasers con-sisting of wire-like active regions, as well as of high index-contrast membrane waveguides. A submilliampere threshold current and a differential quantum efficiency close to 50% from the front facet were achieved in the case of the DR laser. On the other hand, a lateral current injection (LCI) structure, which can be com-bined with the membrane laser, was adopted for the realization of an injection-type membrane laser. The successful continuous wave operation of LCI lasers, prepared on a semiinsulating InP substrate, was achieved with moderately low threshold current at room temperature. Index Terms—DFB laser, distributed reflector (DR) laser, GaInAsP/InP, optical interconnect, optical wiring, semiconduc-tor laser, single-mode laser, Si-on-insulator (SOI) circuits, III–V materials.
IEEE Journal of Selected Topics in Quantum Electronics 01/2011; 17. · 3.78 Impact Factor
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ABSTRACT: The modulation bandwidth enhancement of distributed reflector (DR) lasers with wirelike active regions utilizing optical injection locking is demonstrated both theoretically and experimentally. By the rate equation analysis, it is shown that DR lasers with wirelike active regions realize a low optical injection power and a large bandwidth enhancement under small operation currents. Experimentally, the small-signal bandwidth is increased to >15 GHz at a bias current of 5 mA, which is 4 times smaller than that for conventional edge-emitting lasers. A large signal modulation at 10 Gbps is also performed at the same bias current of 5 mA and voltage swing of 0.4 V(pp), and error-free detection was confirmed under the low-power conditions.
Optics Express 08/2010; 18(16):16370-8. · 3.59 Impact Factor
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ABSTRACT: A room-temperature pulsed operation was demonstrated using lateral current injection-type lasers composed of a 400-nm-thick GaInAsP core layer with compressively strained 5 quantum wells. A threshold current of 105 mA and corresponding density of 1.3 kA/cm(2) (260 A/cm(2) per well) were obtained with the stripe width of 5.4 microm and the cavity length of 1.47 mm. A fundamental transverse mode operation was obtained with the narrower stripe device of 2.0 microm and the cavity length of 805 microm, while the threshold current and corresponding density were 49 mA and 3.0 kA/cm(2), respectively.
Optics Express 08/2009; 17(15):12564-70. · 3.59 Impact Factor
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ABSTRACT: SiO 2 /SiO 2 direct wafer bonding and BCB bonding have been compared to realize membrane GalnAsP wired waveguides on Si Substrate. Bonding environment and pressure were essential for BCB bonding and SiO 2 direct bonding, respectively.
Nano-Optoelectronics Workshop, 2008. i-NOW 2008. International; 09/2008
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ABSTRACT: By applying a double layered EB resist containing C 60 , we could form fine vertical shaped rectangular Si wire waveguide on silicon on insurator (SOI) by parallel plate reactive-ion-etching (RIE). The propagation loss of single-mode Si wire waveguide for TE mode was obtained to be 4.5 dB/cm at 1550 nm, which is the lowest value for those fabricated by parallel plate RIE.
Nano-Optoelectronics Workshop, 2008. i-NOW 2008. International; 09/2008
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ABSTRACT: A lateral current injection laser with a thin (400 nm) core structure grown on a semi-insulating InP substrate was realized and a room-temperature (RT) pulsed operation was obtained. A threshold current of 105 mA, which corresponds to a threshold current density of 1.3 kA/cm<sup>2</sup>, was obtained for a 1.47 mm long Fabry-Perot cavity laser.
Nano-Optoelectronics Workshop, 2008. i-NOW 2008. International; 09/2008
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Shigehisa Arai
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ABSTRACT: With aiming at realization of extremely low power consumption active devices for optical interconnections and photonic integrated circuits (PICs), we have been exploring GaInAsP/InP long wavelength lasers consisting of high index-contrast gratings by low-damage fabrication processes. Moreover, active photonic devices based on high index-contrast waveguides, so called ‘Semiconductor Membrane Lasers,’ have been investigated from their advantage of an enhancement of the optical confinement factor of the active region.
Nano-Optoelectronics Workshop, 2008. i-NOW 2008. International; 09/2008
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ABSTRACT: We fabricated a membrane buried heterostructure distributed feedback
(BH-DFB) laser with an air-bridge structure by selectively etching a
sacrificial layer. A continuous wave (CW) operation under optical
pumping was attained from 10 up to 80 °C, and a minimum threshold
pump power of 4.3 mW was obtained at 20 °C. From the pump-power
dependence of the lasing wavelength, the thermal resistance of this
air-bridge membrane structure was estimated to be 11 K/mW, which is
approximately half that of a previously reported structure (23 K/mW)
fabricated by direct wafer bonding on another InP substrate.
Japanese Journal of Applied Physics 11/2007; 46:L1158-L1160. · 1.06 Impact Factor
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ABSTRACT: Room-temperature continuous-wave operation under optical pumping was
demonstrated using GaInAsP/InP membrane distributed feedback (DFB)
lasers directly bonded on a silicon-on-insulator (SOI) substrate formed
with a rib-waveguide structure. A threshold pump power of 11.3 mW and a
submode suppression ratio of 29 dB were obtained for a cavity length of
140 μm and a stripe width of 1.5 μm. Light output was obtained
through a 500 μm-long SOI waveguide.
Japanese Journal of Applied Physics 11/2007; 46:L1206-L1208. · 1.06 Impact Factor
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ABSTRACT: We characterized the micro-photoluminescence (micro-PL) of GaInAsP/InP single quantum wires (Q-wires) at 6 K. The Q-wires had 6–39-nm lateral widths and a 6-nm vertical thickness and were fabricated by dry etching and regrowth. Micro-PL spectra were clearly observed for all single Q-wires. The spectra revealed a high degree of uniformity along the Q-wires. The PL peak energy showed a systematic blueshift with the reduction of the Q-wire lateral width. The blueshift was attributed to the lateral quantum confinement and strain from a lateral direction, and was 100 meV in a 6-nm-wide Q-wire. Systematic analysis on the PL widths of the Q-wires showed that the PL spectra were broadened by fluctuations of 3 nm in the lateral width of the Q-wire after the dry etching and the regrowth in addition to the broadening caused by the fluctuation in the vertical thickness during the initial film growth and that caused by ion bombardment through a Ti metal mask in the dry etching process. The decreased PL intensities in narrow Q-wires were also analyzed, and they were attributed to decreased PL quantum yield because of damage to the etched sidewalls of the Q-wires during dry etching, and to the absorption cross-sections of the excitation light.
Journal of Applied Physics 11/2007; 102(9):093509-093509-5. · 2.17 Impact Factor
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ABSTRACT: An athermal operation of the lasing wavelength in a membrane buried heterostructure distributed feedback (BH-DFB) laser was demonstrated by adopting a polymer (benzocyclobutene) cladding layer which has a negative temperature coefficient of refractive index. Membrane BH-DFB lasers of core thickness 65 nm were operated under room-temperature continuous-wave conditions. The temperature dependence of the lasing wavelength was measured to be 2.45times10<sup>-2</sup> nm/degC, which is about 20%-30% of that for conventional semiconductor lasers
IEEE Photonics Technology Letters 04/2007; · 2.19 Impact Factor
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ABSTRACT: Distributed feedback lasers with first-order vertical grating based on AlInGaAs-InAs-InP quantum-dash lasers were fabricated by electron beam lithography and Cl<sub>2</sub>-Ar reactive ion etching with an electron cyclotron resonance source. Low threshold currents and single-mode operation with sidemode suppression ratios of 48 dB and a direct modulation bandwidth of 5.5 GHz were demonstrated
IEEE Photonics Technology Letters 04/2007; · 2.19 Impact Factor
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ABSTRACT: We demonstrate 1540-nm-wavelength GaInAsP/InP distributed feedback
lasers, consisting of multiple-quantum-wire active regions with a wire
width of 30 nm, fabricated by electron-beam lithography,
CH4/H2 reactive ion etching, and two-step
organometallic vapor-phase-epitaxial growth processes. By adopting
low-damage fabrication processes for high-mesa stripe structures, a
threshold current as low as 2.1 mA, which corresponds to a threshold
current density of 176 A/cm2, and a differential quantum
efficiency of 16%/facet were obtained under room-temperature
continuous-wave conditions. A sub-mode suppression-ratio of 50 dB at a
bias current of twice the threshold was also achieved.
Japanese Journal of Applied Physics 12/2006; 46:L34-L36. · 1.06 Impact Factor
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ABSTRACT: A room-temperature continuous-wave operation under optical pumping was demonstrated with GaInAsP/InP membrane buriedheterostructure (BH) distributed-feedback (DFB) laser directly bonded on an SOI substrate. A threshold pump power of 2.8 mW and a sub-mode suppression ratio of 28 dB were obtained with a cavity length of 120 microm and a stripe width of 2 microm.
Optics Express 10/2006; 14(18):8184-8. · 3.59 Impact Factor
